Generally, unlike a primary battery incapable of being recharged, a secondary battery may be repeatedly charged and discharged. Recently, a high power secondary battery using a non-aqueous electrolyte having high energy density has been developed. For example, U.S. Pat. No. 6,193,765 discloses a battery equipping current collecting elements formed as a plate instead of as a conventional tab.
When one battery cell is packaged into a pack shape it forms a low capacity battery that may be used as a power source for various portable small electronic devices such as cellular phones, laptop computers, and camcorders. When several tens of the battery cells are connected in serial or in parallel, a high capacity secondary battery is formed that may be used as a power source for driving motors such as in a hybrid automobile.
A secondary battery may be fabricated into various shapes such as a cylindrical, a prismatic or a pouch shape. The secondary battery includes an electrode assembly including a positive electrode, a negative electrode and a separator interposing between them wound spirally (or in a jelly roll configuration) and inserted into a case. The case is mounted with a cap assembly formed with an outer terminal to provide a battery.
The positive electrode and the negative electrode of the secondary battery are each equipped with a conductive tab which collect a current generated from an electrode group during the battery operation and induce it to an external terminal.
However, conventional secondary batteries have a structure that may prevent an electrolyte from being successfully infused into an electrode group because the injection of an electrolyte into a case and its subsequent infusion proceeds too slowly.
Illustrating in more detail, an electrolyte infusion in the conventional art has been commonly performed by capillary phenomena enabling an electrolyte to be soaked up into the electrode group. In these batteries, a negative collecting plate at the bottom of a case acts to slow down the infusion process by impeding the capillary phenomena.
This problem may be worse in a high power secondary battery designed to drive a motor for a machine such as a hybrid electric vehicle (HEV), because the battery is fabricated to satisfy high-quality battery characteristics such as a high output.